Heads up if you plan to head into the water at Renforth Beach in Rothesay.

Public Health recently posted a blue-green algae advisory at the beach.

“Blue-green algae (cyanobacteria) blooms have been seen in this water,” said the sign.

Blue-green algae, also known as cyanobacteria, are naturally occurring bacteria found in many New Brunswick ponds, lakes, and rivers.

The bacteria are not normally visible, but under certain conditions, can increase in numbers to form surface blooms of benthic mats.

While not all blue-green algae are harmful, some can produce toxins that can cause skin, eye and throat irritation.

The algae are most commonly blue-green in colour as its name suggests, but surface blooms can also be green, red, brown, or yellow.

Blooms can also appear as mats that can look like clumps of vegetation that appear black, brown or dark green in the water.

On the shoreline, they may be brown or grey once they have dried and can sometimes be attached to rocks or aquatic vegetation found floating in the water.

Public Health says you and your pets should stay out of the water in areas where there are visible blooms or mats.

Pets should also be kept away from the mats as they can be toxic and potentially lethal if eaten.

Blue-green advisories are in effect for more than 20 waterways across the province, including the Saint John River between Woodstock and Fredericton, the Kennebecasis River at the Rothesay Yacht Club, Belleisle Bay, Grand Lake, and Washademoak Lake.

Public Health said once an advisory is posted, it will remain on the list indefinitely.

“Although each summer the area of water indicated may not have cyanobacteria blooms, they are left on the list for visitors to be aware that they could possibly recur since the area has had cyanobacteria blooms in the past,” said the department’s website.

You can find more details about blue-green algae by clicking here.